1. Technical Field
Embodiments of the present invention relate generally to systems and methods for cooling electric machines, and specifically to cooling electric machines with direct winding cooling.
2. Background of Related Art
The increasing demand for electrical power sources for, for example, hybrid electric vehicle (HEV) and electric vehicle (EV) power trains has created a need for high torque density electric machines. In addition to HEV and EV passenger cars, other applications that require high torque density machines include, for example and not limitation, off road construction equipment, freight trucks, military ships, and electric actuators for flight control surfaces in aircrafts. Currently, a limiting factor for consistent power output is the thermal degradation of the windings. In other words, the heat in the windings caused by generating higher power outputs increases the resistance in the windings, and melts insulation, among other things.
Conventionally, the techniques employed to improve the thermal transport processes in small scale (e.g., less than 100 kW) electrical machines has been focused on improving the internal and external air flow across the electrical machine. Other methods have attempted to improve flow through the machine, but generally rely on conduction to transfer heat from the windings to the stator, reducing efficiency.
Direct lamination cooling (DLC), for example, provides cooling by passing coolant directly through channels in the stator. Unfortunately, this configuration changes the flux paths inside the stator. In addition, DLC primarily removes heat from the stator and, thus, relies on conduction from the windings to the stator to cool the windings. Phase change cooling, utilizing the heat of vaporization of the coolant, has been used for the thermal management of large scale electrical machines (i.e., on the order of several hundred megawatts). Unfortunately, large temperature gradients arise due to the increased heat transfer from evaporative cooling resulting in poor reliability in small scale applications. In addition, the design and implementation of advanced cooling in electric machines in general, and smaller machines in particular, is limited.
What is needed, therefore, is an integrated design tool, system, and method utilizing advanced cooling techniques. In some embodiments, the system should include an integrated thermal model including novel advanced cooling technologies. The integrated, advanced, thermal model can be used in conjunction with optimization techniques to provide improved systems and methods for electric machines with the novel cooling techniques. In some embodiments, the integrated model, in conjunction with optimization techniques, can be used to access system sizing and cooling requirements, among other things.